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:Ce using PHITS track-structure simulationsHirata, Yuho; Kai, Takeshi; Ogawa, Tatsuhiko; Matsuya, Yusuke; Sato, Tatsuhiko; Watanabe, Kenichi*; Kato, Takumi*; Kawaguchi, Noriaki*; Yanagida, Takayuki*
Radiation Measurements, 193, p.107651_1 - 107651_8, 2026/04
Times Cited Count：0CaF:Ce has a high potential to be used as a dosimeter due to its high optically stimulated luminescence (OSL) intensity. However, when phosphors such as CaF:Ce are irradiated with swift ions, the OSL intensity per dose decreases due to quenching effects. Traditionally, quenching effects in phosphors have been evaluated based on energy deposition density, using linear energy transfer (LET) as a metric. However, the relationship between quenching effects and LET varies with ion type, complicating unified evaluations. The track structure in PHITS can precisely simulate the radiation interactions. In this study, we simulated the detector response of CaF:Ce irradiated with swift-ions and compared these results with experimental data. The comparison suggests that the quantum yield of OSL is a critical parameter influencing the quenching effect in CaF:Ce. These findings are expected to contribute to the development of improved phosphor detectors.
Doda, Norihiro; Kato, Shinya; Uwaba, Tomoyuki; Tanaka, Masaaki; Nakamine, Yoshiaki*; Igawa, Kenichi*; Iida, Masaki*
Proceedings of 21st International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-21) (Internet), 14 Pages, 2025/08
Accurate evaluation of reactivity feedback due to core deformation during power increases in sodium-cooled fast reactors requires comprehensive modeling of the interactions among neutronics, thermal-hydraulics, and core mechanics. To accurately consider these interactions, JAEA has developed an evaluation method that combines multiple analysis codes that model these phenomena in detail. In this study, the evaluation method was applied to the core analysis of the FFTF LOFWOS Test #13, and the analysis results of net reactivity were compared with the test results. The sensitivity analysis results of the core structural design parameters showed that the core bowing behavior has a significant effect on the temporal variation of net reactivity.
Kato, Masaru*; Zheng, J.*; Deng, Y.*; Saito, Fumie*; Unuma, Yuki*; Oka, Sayuki*; Tamura, Kazuhisa; Yagi, Ichizo*
ACS Catalysis, 15(10), p.7710 - 7719, 2025/04
Times Cited Count：3 Percentile：75.57(Chemistry, Physical)
Pu
Am
)O
Yokoyama, Keisuke; Watanabe, Masashi; Usui, Akane; Seki, Takayuki*; Onishi, Takashi; Kato, Masato
Nuclear Materials and Energy (Internet), 42, p.101908_1 - 101908_6, 2025/03
Times Cited Count：0 Percentile：0.00(Nuclear Science & Technology)Oxygen potential of high Am content MOX, (UPuAm)O, was measured at 1273 K, 1473 K, 1573 K, and 1623 K. by gas equilibrium method using thermogravimeter. Comparing the measured data with the literature data, it was found that the addition of 15% Am increases the oxygen potential of (U, Pu)O
by 100-150 kJ/mol for the same Pu content and O/M ratio. The proportion of cations in the stoichiometric composition was determined as (U
U
Pu
Am
)O, assuming the presence of Am
and partial oxidation of U
to U
. The relationship between oxygen partial pressure and deviation x from stoichiometry in (UPuAm)O was analyzed by defect chemistry model. The equation to represent the O/M ratio was derived as a function of temperature and oxygen partial pressure. A part of this study includes the results of MEXT Innovative Nuclear Research and Development Program Grant Number JPMXD0219214921.
Ito, Kengo*; Takahashi, Shin*; Kato, Chizu*; Fukutani, Satoshi*; Matsumura, Tatsuro; Fujii, Toshiyuki*
Journal of Radioanalytical and Nuclear Chemistry, 334, p.2467 - 2475, 2025/02
Times Cited Count：0 Percentile：0.00(Chemistry, Analytical)In this study, the solvent extraction behavior of tin (Sn), specifically 
Sn, from high-level radioactive waste was evaluated using six different extractants in a HNO
system. Among the tested extractants, N,N-Didodecyl-2-hydroxyacetoamide (HAA) exhibited higher efficiency, still not sufficient for industrial implementation. In systems where HCl was added to HNO, both tributyl phosphate (TBP) and N,N,N,N'-tetra-2-ethylhexyl diglycolamide (TEHDGA) achieved D
values greater than 1 at 
1 M HCl. However, due to practical challenges in industrial applications, HAA extraction in HNO systems, particularly at low Sn concentrations (0.0008 M), may provide a more effective solution for Sn recovery.
Nakamura, Satoshi; Ishii, Sho*; Kato, Hitoshi*; Ban, Yasutoshi; Hiruta, Kenta; Yoshida, Takuya; Uehara, Hiroyuki; Obata, Hiroki; Kimura, Yasuhiko; Takano, Masahide
Journal of Nuclear Science and Technology, 62(1), p.56 - 64, 2025/01
Times Cited Count：1 Percentile：27.40(Nuclear Science & Technology)A dissolution method for analyzing the elemental composition of fuel debris using the sodium peroxide (Na
O) fusion technique has been developed. Herein, two different types of simulated debris materials (such as solid solution of (Zr,RE)O and molten core-concrete interaction products (MCCI)) were taken. At various temperatures, these debris materials were subsequently fused with NaO in crucibles, which are made of different materials, such as Ni, AlO, Fe, and Zr. Then, the fused samples are dissolved in nitric acid. Furthermore, the effects of the experimental conditions on the elemental composition analysis were evaluated using inductively coupled plasma-atomic emission spectroscopy (ICP-AES), which suggested the use of a Ni crucible at 923 K as an optimum testing condition. The optimum testing condition was then applied to the demonstration tests with Three Mile Island unit-2 (TMI-2) debris in a shielded concrete cell, thereby achieving complete dissolution of the debris. The elemental composition of TMI-2 debris revealed by the proposed dissolution method has good reproducibility and has an insignificant contradiction in the mass balance of the sample. Therefore, this newly developed reproducible dissolution method can be effectively utilized in practical applications by dissolving fuel debris and estimating its elemental composition.
Ito, Kengo*; Morita, Misaki*; Araki, Yuta*; Kato, Chizu*; Fukutani, Satoshi*; Matsumura, Tatsuro; Fujii, Toshiyuki*
Solvent Extraction Research and Development, Japan, 32(1), p.53 - 62, 2025/00
Times Cited Count：0 Percentile：0.00(Chemistry, Multidisciplinary)Rhodium (Rh) and Palladium (Pd) in high-level radioactive waste are primarily fission products. This Study focused on understanding the extraction behavior of these platinum group elements (PGEs) using the novel extractants 
-hexaoctylnitriloacetamide (HONTA) and alkyl diamideamine (ADAAM). Both extractants showed affinity for Pd, with distribution coefficients significantly exceeding 1, demonstrating their effectiveness in Pd separation. In contrast, the distribution coefficients for Rh were consistently below 10 
, indicating low extraction efficiency from nitric acid. However, by leveraging the salting-out effect with calcium nitrate hydrate, a distribution coefficient of 
570 for Rh was achieved using HONTA. To overcome the difficult back-extraction of PGEs with HONTA, experiments were conducted using HEDTA and thiourea. Back-extraction with HEDTA in high-concentration nitric acid (2M) resulted in 90% extraction of Pd, while thiourea-based back-extraction with nitric acid yielded over 40% extraction for Rh, with the maximum of 62.7% achieved using hydrochloric acid.
Kato, Yuto*; Sasaki, Takayuki*; Tonna, Ryutaro*; Kobayashi, Taishi*; Okamoto, Yoshihiro
Applied Geochemistry, 175, p.106196_1 - 106196_9, 2024/11
Times Cited Count：3 Percentile：36.73(Geochemistry & Geophysics)Yoshimune, Wataru*; Higuchi, Yuki*; Song, F.; Hibi, Shogo*; Matsumoto, Yoshihiro*; Hayashida, Hirotoshi*; Nozaki, Hiroshi*; Shinohara, Takenao; Kato, Satoru*
Physical Chemistry Chemical Physics, 26(47), p.29466 - 29474, 2024/11
Times Cited Count：6 Percentile：76.16(Chemistry, Physical)
AmO at 1473, 1573, and 1673 KWatanabe, Masashi; Yokoyama, Keisuke; Vauchy, R.; Kato, Masato; Sugata, Hiromasa*; Seki, Takayuki*; Hino, Tetsushi*
Journal of Nuclear Materials, 599, p.155232_1 - 155232_5, 2024/10
Times Cited Count：3 Percentile：65.33(Materials Science, Multidisciplinary)Oxygen potential data of UAmO were measured at 1473, 1573, and 1673 K by thermogravimetry. In U
An
O, where An stands for Pu or Am, and for a given value of y and Oxygen/Metal ratio, the oxygen potential of UAmO is higher than that of UPuO. The valence of cations in the hypostoichiometric region is similar to that of Nd-doped UO. At the stoichiometric composition, it is estimated to be Am, U, and U (for charge compensation of Am). The experimental data were analyzed using a defect chemistry model, and a relationship connecting the oxygen-to-metal ratio, the temperature, and the equilibrium oxygen partial pressure was proposed.
Kato, Hiroyuki S.*; Muroyama, Mizuho*; Kobayakawa, Nano*; Muneyasu, Riku*; Tsuda, Yasutaka; Murase, Natsumi*; Watanabe, Seiya*; Yamada, Takashi*; Kanematsu, Yusuke*; Tachikawa, Masanori*; et al.
Journal of Physical Chemistry Letters (Internet), 15(43), p.10769 - 10776, 2024/10
Times Cited Count：2 Percentile：33.26(Chemistry, Physical)Ito, Kengo*; Kawakami, Takahiro*; Kato, Chizu*; Fukutani, Satoshi*; Matsumura, Tatsuro; Fujii, Toshiyuki*
Journal of Radioanalytical and Nuclear Chemistry, 333(10), p.5183 - 5189, 2024/10
Times Cited Count：1 Percentile：27.40(Chemistry, Analytical)Solvent extraction behaviors of Se (VI) from nitric acid solutions were investigated with multiple extractants used for uranium, plutonium, minor actinides, and rare earthelements separation processes from high-level liquid waste. During the processes, Se remained in the residual aqueous solutions, as all extractants showed distributionratios 
1. In contrast, Se showed distribution ratios 1 with 
-phenylenediamine in dilute nitric acid ( 2 M HNO), octanol as the organic phase, and concentrated nitric acid (8 M HNO) for back extraction, suggesting a potential new single separation process and recovery of Se.
Machida, Masahiko; Yamada, Susumu; Kim, M.; Tanaka, Satoshi*; Tobita, Yasuhiro*; Iwata, Ayako*; Aoki, Yuto; Aoki, Kazuhisa; Yanagisawa, Kenichi*; Yamaguchi, Takashi; et al.
RIST News, (70), p.3 - 22, 2024/09
Inside the Fukushima Daiichi Nuclear Power Plant (1F), there are many locations with high radiation levels due to contamination by radioactive materials that leaked from the reactor. These pose a significant obstacle to the smooth progress of decommissioning work. To help solve this issue, the Japan Atomic Energy Agency (JAEA), under a subsidy from the Ministry of Economy, Trade, and Industry's decommissioning and contaminated water management project, is conducting research and development on digital technologies to improve the radiation environment inside the decommissioning site. This project, titled "Development of Technology to Improve the Environment Inside Reactor Buildings (Enhancing Digital Technology for Environment and Source Distribution to Reduce Radiation Exposure)," began in April of FY 2023. In this project, the aim is to develop three interconnected systems: FrontEnd, Pro, and BackEnd. The FrontEnd system, based on the previously developed 3D-ADRES-Indoor (prototype) from FY 2021-2022, will be upgraded to a high-speed digital twin technology usable on-site. The Pro system will carry out detailed analysis in rooms such as the new office building at 1F, while the BackEnd system will serve as a database to centrally manage the collected and analyzed data. This report focuses on the FrontEnd system, which will be used on-site. After point cloud measurement, the system will quickly create a 3D mesh model, estimate the radiation source from dose rate measurements, and refine the position and intensity of the estimated source using recalculation techniques (re-observation instructions and re-estimation). The results of verification tests conducted on Unit 5 are also presented. Furthermore, the report briefly discusses the future research and development plans for this project.
Kato, Akane; Shirafuji, Masaya; Suekane, Yurika; Shimizu, Yasuyuki; Kitao, Takahiko
Proceedings of 65th Annual Meeting of the Institute of Nuclear Materials Management (Internet), 9 Pages, 2024/07
Tokai Reprocessing Plant (TRP) started to recover those remaining nuclear materials from main process in reprocessing facility (Flush-out) as a first step of decommissioning. Flush-out plan is conducted by three steps for recovering sheared powder (Stage A), Pu (Stage B) and U (Stage C). Stage A for recovering sheared powder was implemented from June to September 2022. As the next step of Flush-out plan, Stage B and Stage C, were implemented from March 2023 in stepwise. Stage B is to transfer Pu solution from storage material balance area (MBA) to HALW storage as retained waste, and stage C is to fabricate Uranium trioxide powder from U solution. Since these activities for flush-out are different from conventional reprocessing operation, TRP should overcome the subject for the establishment of appropriate material control and accountancy (MC&A) method and new safeguards measures implemented by IAEA. In this paper, we report about Pu and U recovery process and relevant MC&A and safeguards measures in the Flush-out.
Kato, Yukitaka*; Yamano, Hidemasa
Dai-28-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 5 Pages, 2024/06
The research committee of energy storage technologies toward carbon neutrality developed four suggestions: 1) Development of energy storage best mix, 2) Transformation to green society, 3) utilization of heat storage technologies, and 4) Development of energy storage strategy beyond 2050. This paper describes suggestion 2) Transformation to green society by zero-carbon energy, 3) further utilization of heat storage technologies in the industry and civil sectors, and 4) Development of energy storage strategy toward achievement of carbon negative emission beyond 2050.
Kato, Yukitaka*; Yamano, Hidemasa
Dai-28-Kai Doryoku, Enerugi Gijutsu Shimpojiumu Koen Rombunshu (Internet), 5 Pages, 2024/06
The research committee of energy storage technologies toward carbon neutrality developed four suggestions: 1) Development of energy storage best mix, 2) Transformation to green society, 3) utilization of heat storage technologies, and 4) Development of energy storage strategy beyond 2050. This paper describes suggestion 1) Development of energy storage best mix in response to large-scale deployments of variable renewable energy.
molecule generation from dissociatively adsorbed water on TiO through photoexcitationKato, Koichi*; Nagatsuka, Naoki*; Fukutani, Katsuyuki
Journal of Physical Chemistry C, 128(20), p.8188 - 8198, 2024/05
Times Cited Count：2 Percentile：23.26(Chemistry, Physical)Kato, Masato; Oki, Takumi; Watanabe, Masashi; Hirooka, Shun; Vauchy, R.; Ozawa, Takayuki; Uwaba, Tomoyuki; Ikusawa, Yoshihisa; Nakamura, Hiroki; Machida, Masahiko
Journal of the American Ceramic Society, 107(5), p.2998 - 3011, 2024/05
Times Cited Count：8 Percentile：47.23(Materials Science, Ceramics)
-phenylmaleimideYamazaki, Shun*; Kaneko, Naoya*; Kato, Atsuya*; Watanabe, Kohei*; Aoki, Daisuke*; Taniguchi, Tatsuo*; Karatsu, Takashi*; Ueda, Yuki; Motokawa, Ryuhei; Okura, Koki*; et al.
Polymer, 298, p.126846_1 - 126846_11, 2024/04
Times Cited Count：6 Percentile：59.68(Polymer Science)Higuchi, Yuki*; Yoshimune, Wataru*; Kato, Satoru*; Hibi, Shogo*; Setoyama, Daigo*; Isegawa, Kazuhisa*; Matsumoto, Yoshihiro*; Hayashida, Hirotoshi*; Nozaki, Hiroshi*; Harada, Masashi*; et al.
Communications Engineering (Internet), 3, p.33_1 - 33_7, 2024/02
